Power operated rotary knives are widely used in meat processing facilities for meat cutting and trimming operations. Power operated rotary knives also have application in a variety of other industries where cutting and/or trimming operations need to be performed quickly and with less effort than would be the case if traditional manual cutting or trimming tools were used, e.g., long knives, scissors, nippers, etc. By way of example, power operated rotary knives may be effectively utilized for such diverse tasks as taxidermy; cutting and trimming of elastomeric or urethane foam for a variety of applications including vehicle seats; and tissue removal or debriding in connection with medical/surgical procedures and/or tissue recovery from a body of a human or animal donor.
Power operated rotary knives typically include a handle assembly and a head assembly. The head assembly includes an annular blade housing and an annular rotary knife blade supported for rotation by the blade housing. The head assembly of a power operated rotary knife also includes a gearbox housing which supports a gear train for rotatably driving the rotary knife blade. In some instances, the gear train supported in the gearbox housing may comprise a single gear, in other instances; the gear train may include a plurality of gears for driving the rotary knife blade. The gear train is part of a drive assembly for the power operated rotary knife, the gear train being internal to the rotary knife. Power operated rotary knives having various gear train embodiments including a gear train comprising a single gear and a gear train including a plurality of gears are disclosed in U.S. patent application Ser. No. 13/189,925 to Whited et al., filed on Jul. 25, 2011 (“the '925 application”). The '925 application is assigned to the assignee of the present application and is incorporated herein, in its entirety, by reference.
The drive assembly also includes components external to the power operated rotary knife including an external drive motor and a flexible shaft drive transmission. Motive or rotational power which drives the gear train of the power operated rotary knife is typically provided from an external drive motor and transmitted through a flexible shaft drive transmission. The flexible shaft drive transmission typically includes an elongated drive transmitting shaft which rotates within an outer casing. The elongated drive transmitting shaft includes a driven fitting at one end of the drive transmitting shaft that engages and is rotated by the mating drive fitting of the drive motor and a drive fitting at the opposite end of the drive transmitting shaft that engages and rotates a mating driven fitting of the gear train of the power operated rotary knife. Rotation of the drive transmitting shaft by the external motor rotates the gear train of the power operated rotary knife, which, in turn, rotates the rotary knife blade.
The outer casing of a typical flexible shaft drive transmission includes a first, motor end coupling at one end of the outer casing which is adapted to be releasably coupled to a mating coupling of the drive motor, such that, when the motor end coupling and the drive motor coupling are engaged, the driven fitting of the drive transmitting shaft engages and is rotationally driven by the drive fitting of the drive motor. A second, handle assembly coupling at the opposite end of the outer casing is adapted to be releasably coupled to the handle assembly of the power operated rotary knife such that the drive fitting of the drive transmitting shaft engages and drives the driven fitting of the gear train of the power operated rotary knife.
Typically, lubricant, such as lubricant grease, is disposed between the outer casing and the drive transmitting shaft of the flexible shaft drive transmission. One recurring problem with respect to the handle assembly coupling end of the flexible shaft drive transmission is that lubricant would tend to leak out between the shaft and the outer casing. The drive motor is typically mounted on a hanger positioned above the work area where a power operated rotary knife is manipulated by an operator to trim or cut a product. Thus, motor end coupling of the flexible shaft drive transmission is typically at a higher vertical position than the handle assembly coupling end of the flexible shaft drive transmission. Because of the lower vertical position of the handle assembly coupling, gravity causes the lubricant to migrate or drain toward the handle assembly coupling. Thus, leakage of lubricant between the drive transmitting shaft and the outer casing at the handle assembly coupling end of the flexible shalt drive transmission typically is a much greater problem than at the motor coupling end. Various attempts have been made to minimize lubricant leakage through the handle assembly coupling end of the shaft drive transmission such as, for example, the structures disclosed in U.S. Pat. No. 6,3514,949 to Baris et al. and U.S. Pat. No. 7,153,202 to Rosu et al., both of which are assigned to the assignee of the present disclosure. However, the problem persisted.
At least in part because of the loss of lubricant through leakage, in prior flexible shaft drive transmissions, the drive transmitting shaft would have to be periodically removed from the outer casing to inject new lubricant into the transmission. If sufficient lubricant leaks out between the drive transmitting shaft and the outer casing, undesirable friction and heat will be generated by contact between the rapidly rotating drive transmitting shaft and the stationary outer casing. Without the periodic disassembly of the shaft drive transmission to inject new lubricant into the outer casing of prior flexible shaft drive transmissions, the operating life of the drive transmitting shaft and the outer casing would be significantly reduced because of increased heat and wear resulting from lack of sufficient lubricant. However, periodic maintenance of the shaft drive transmission, like any required maintenance, is costly in terms of both labor required for maintenance and downtime of the equipment.
An additional problem with prior flexible shaft drive transmission stemmed from the fact that the drive transmitting shaft was not secured within the casing. Specifically, when the motor end coupling is released from the drive motor coupling, the drive transmitting shaft will tend to slide out of the outer casing. This is both inconvenient for the operator of the power operated rotary knife and can result in contamination of the flexible shaft drive transmission.